Two-temperature refrigerating system



7, 1948. L. w. ATCHISON 2,455,850

' TWO-TEMPERATUREREFRIGERATINQ SYSTEM Filed May 5. 1947 Invehtor: Leonard WAtch'ison,

His Attorney.

Patented Dec. 7, 1948 7 v TWO-TEMPERATURE SYS York REFRIGERATING TEM Leonard Atchison, Erie, Pa., asslgnor to General Electric Company, a corporation of New Application May 5, 1947, Serial No. 145,939

3 Claims. (CL- 62-115) My invention relates to refrigerating systems and particularly to systems includin a plurality of evaporators for operation at different tempera tures.

'It is an object of my invention to provide an improved refrigeratin apparatus including primary and secondary refrigerating systems wherein the primary system includes two evaporators having a flow-controlling device therebetween.

Further objects and advantages of myinvention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of my invention reference may be had to the accompanying drawing the single figure of which shows schematically a refrigerating system including an embodiment of my invention.

Referring to the drawing, the refrigerating apparatus includes a primary refrigerating system and a secondary refrigerating system. The primary refrigerating system includes a suitable compressor I, a condenser 2, and two evaporators 3 and 4. supplied to the evaporator 3 through a restricted tube 5, sometimes referred to as a capillary tube. vaporized refrigerant collects in a header 6 and is withdrawn by the compressor through a suction line I. The capillary tube and thesuction line are arranged in heat exchange relationship along a portion of their lengths in order to vaporize liquid refrigerant in the suction line and prevent its being drawn into the compressor and also in order to supply additional cooling for the liquid refrigerant passing through the capillary tube.

The evaporators 3 and 4 are arranged in serie relationship in the primary refrigerating system. In order to maintain a constant pressure in the evaporator 3, a constant back pressure valve 8 is placed in the primary refrigerating system between the evaporator 3 and the evaporator 4. The valve 8 includes a housing 9 with which the evaporators 3 and 4 communicate. Within the Condensed refrigerant is 2 toward its open position. The bellows I2 is placed in communication with a second bellows 14, which is fixed to the outside of the housing 9, through housing 9 there is provided a valve seat Ill with v an opening H5 in the housing, In order to provide for adjustment of the pressure to be maintained by the valve an adjusting screw I6 is threaded into a bracket I1 secured to the outside of the housing 9 and bearsagainst the bellows l4. Since the bellows I2 and the bellows l4 are in communication through the openin 15, adjustment of the screw l6 affects the pressure exerted by the bellows l2, and accordingly varies the pressure at which the valve opens. The two bellows are charged with any suitable fluid, such as nitrogen.

The secondary refrigerating system includes a secondary condenser l8 and a secondary evaporator [9; which are connected in a closed refrigerating system. In order to extract heat from the refrigerant in the secondary system, the secondary condenser is arranged in heat exchange relationship with the primary evaporator 3. The secondary evaporator may be used, for example, to cool the food storage compartment of a twotemperature refrigerator. It is often desirable to operate the evaporator used for this purpose on a defrosting cycle, that is, the temperature is arranged to rise sufficiently above 32 F. during the off-period of the apparatus to cause a melting of any frost which may have accumulated during the on-period of the apparatus. In order to facilitate the operation of the secondary system on a defrosting cycle, the primary evaporator 3 is made of a small thermal mass. Hence any refrigerating capacity stored in the primary evaporator 3 during the operating period of the refrigerating apparatus will be dissipated rapidly during the off-period, and refrigeration by the secondary refrigerating system will terminate a very short time after the compressor l is shut down. This permits the temperature of the secondary evaporator H! to rise above 32 F. soon after the compressor I is shut down and insures that any frost which has accumulated on the secondary evaporator I!) will be removed before the next operating period of the refrigerating apparatus.

In orderto further facilitate the operation of the secondary refrigerating system on a defrosting cycle, the primary evaporator 3 is arranged with a substantial slope so that liquid refrigerant contained therein when the-compressor stops will drain rapidly from the primary evaporator 3 and will not be available for further refrigeration of the secondary system. a

The compressor I is driven by an electric motor 20 or any other suitable source of motive power, and power is supplied to the motor 20 through lines 2|. In order to control the supply of power to the motor and hence the operation of the compressor a switch 22 is arranged in the line 2|, and the operation of the switch is govemed by a thermostatic bulb 28 which is located so as to be responsive to the temperature of the primary evaporator 3. The bulb 23 is connected by a suitable tube 26 to a bellows'w for moving .the switch to its open and closed positions.

veniently be used for refrigerating the IOW'tGlllperature or freezing zone of a two-temperature refrigerator. Because of the construction of the evaporator 3 and its arrangement in the system, evaporator 3 may be operated on a defrosting cycle.

WhileI have described a specific embodiment of my invention, I do'not desire my invention to be limited to the specific construction shown and I intend by the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by I Letters Patent of the United States is:

1. Refrigerating apparatus comprisinga primary refrigerating system including two evaporators, means for supplyingrefrigerant to said evaporators in series, a valve connected in said Evaporator Q will system between said evaporators for maintaining a constant pressure in one of said evaporators, and a secondary refrigerating system in- -cluding a secondary condenser and a secondary evaporator, said secondary condenser being arranged in heat exchange relationship with said one of said first-mentioned evaporators.

2. Refrigerating apparatus comprising a primary refri erating system including two evaporators,vmeans for supplying refrigerant to said evaporators in series, a valve connected in said system between said evaporators for maintaining a constant pressure in one of said evapor tors, said one of said evaporators being sloped 1: provide, rapid drainage of refrigerant from sai one evaporator, and a secondary refrigerating system including a secondary condenser and a secondary evaporator, said secondary'condenser being arranged in heat exchange relationship with said one of said first-mentioned evaporators.

3. Refrigerating apparatus comprising a primary refrigerating system including two evaporators, means for supplying refrigerant to said evaporators in series, a valve connected in" said system between said evaporators for maintaining a constant pressure in one of said evaporators, and a secondary refrigerating system in cluding a secondary condenser and a secondary evaporator, said secondary condenser being arrangedrin heat exchange relationship with said one of said first-mentioned evaporators, said one of said first-mentioned evaporators being oflsmali thermal mass whereby refrigeration by said sec ondary system is terminated shortly after the supply of refrigerant to said first-mentioned evaporators is terminated. LEONARD W. ATCHISON.

vNo references cited. 

